Cannabis and Canadian youth: evidence, not ideology.

A recent United Nations Children’s Fund study on the well-being of children1 found that Canadian adolescents (aged 11 to 15 years) have the highest rate of cannabis use among the 29 advanced economies of the world; an estimated 28% had used cannabis at least once in the past year. The 2011 Canadian Alcohol and Drug Use Monitoring Survey, which surveyed older youth, found slightly lower rates of cannabis use; about 21% had used cannabis at least once in the past year.2 Of concern, a considerable percentage of the Canadian youth who have used in the past year are daily or weekly users—approximately 22% of boys and 10% of girls.3 The high rate of cannabis use by youth in Canada is worrisome. Recent evidence shows that there are substantial risks to youth who are regular cannabis users. They appear to be at increased risk of having problematic cannabis use and developing cannabis addictions as compared with adult users.4 They are also at risk of social dysfunction, including work and school impairment.5 Also, the developing adolescent brain might be particularly vulnerable to regular exposure to cannabis.6 One recent study found that adults who used cannabis regularly in their teen years experienced a 5to 8-point drop in their IQ scores, which persisted into midlife, even if they stopped using cannabis when they reached adulthood.7 Finally, heavy cannabis use in adolescence is a risk factor for psychosis and might contribute to the development of a persistent psychotic disorder.8-10 It is important to note that Canadian teens are not using all substances more often than their counterparts in other countries; their use of tobacco and alcohol falls in the low and average range, respectively.1 The explanation for the international variation in usage rates for these licit and illicit substances is complex. Factors include social and cultural norms, drug availability, and national drug policy (prevention, treatment, and enforcement).